Use task's userId to obtain PackageManager instance

This is a follow up to Ia4b2cf80278e49fe1b6d26ea99d4be48110c7232 with a
proper fix. Instead of using MATCH_UNINSTALLED_PACKAGES, which worked
because the package is technically "uninstalled" for the current user
(because it's installed for another user), this change now builds a user
context using the userId in TaskInfo, and whose PackageManager can now
obtain the ActivityInfo without additional flags.

Bug: 354884302
Fix: 355306146
Test: with HSUM enabled, app name and icon can be obtained through
PackageManager without crashing
Flag: EXEMPT bugfix

Change-Id: I54c3a4332dbb330b0c4ff9df0e86ec038716f7ff